Post deflection color purity correcting device for a color tv cathode ray tube and system using the same



June 14, 1960 s. L. REICHES 2,941,102

PQST DEFLECTION COLOR PURITY CORRECTING DEVICE FOR A COLOR TV CATHODE RAY TUBE AND SYSTEM USING THE SAME Filed July 26, 1956 3 Sheets-Sheet l BY 407 6 c/Qz forrzqg June 14, 1960 s. 1.. REICHES 2,941,102

POST DEFLEICTION COLOR PURITY CORRECTING DEVICE FOR A COLOR TV CATHODE RAY TUBE AND SYSTEM USING THE SAME Filed July 26, 1956 3 Sheets-Sheet 2 INVENTOR. 6'02 13. Rez'cizes BY M 0 22 202 72429 June 14-, 1960 s, 5 2,941,102

POST DEF'LECTION COLOR PURITY CORRECTING DEVICE FOR A COLOR TV CATHODE RAY TUBE AND SYSTEM USING THE SAME Filed July 26, 1956 3 Sheets-Sheet 5 @GGOO F2 /0a P5 /06 Fig /0( 631/04 @406 Fig /0/ 501 L Rf/(fifj INVENTOR.

I 2,941,102 Patented June 14, 1960 POST DEFLECTION COLOR PURITY CORRECT- ING DEVICE FOR A COLOR TV CATHODE RAY TUBE AND SYSTEM USING THE SAME Sol L. Reiches, 6900 Wade Park Ave., Shaker Heights 3, Ohio Filed July 26, 1956, Ser. No. 600,314

5 Claims. (Cl. 313-77) This application is a continuation in part of my copending application entitled Post Deflection Color Purity Correcting Device for a Color TV Cathode Ray Tube, Serial Number 564,197, filed February 8, 1956, now

abandoned, and assigned to the same assignee as this application.

My invention relates to an improved post deflection color purity correcting device for a cathode ray tube and a system using the same, characterized by the ability in asingle unit to accomplish the same color purity correction which has heretofore. required separate magnet assemblies, one embracing the neck of the cathode ray tube and the other located at the bell portion adjacent the viewing screen.

One of the problems incident to the use of the color image reproducing tubes, such as the so-called shadow mask type, the post acceleration tube, the apple tube or the focus mask tube to reconstitute the color picture of a television transmission is that of achieving color purity. The shadow mask tube, for example, uses three electron guns to produce ray beams modulated in accord with the three primary color components of the image to be reproduced. Faithful reproduction of the original colors demands that each of these beams energize only the phosphor dots producing illumination of the color for which the respective beam is modulated. In the manufacture of tubes of this kind optical methods are used to simulate the action of the respective electron guns and thereby locate the respective phosphor dots required for reproduction of the various colors. These optical methods are based on the premise that the electron beams act as if each originates from a design center or point during deflection. In operation, however, the electron streams do not behave exactly as the optical methods predict and other departures from the theoretical ideal require the use of adjustable means to compensate for these departures and restore the color purity of the image. Similar problems arise in connection with the other types of color television tubes for operation is dependent in at least some measure on the electron streams acting as if originating from a design center or point during deflection.

Heretofore, color purity correction has been achieved by the use of a purity magnet assembly located in the neck of the cathode ray tube. Such a unit acts on the electron beams before they are deflected in sweep motions .and can at most provide some measure of correction for the departures of the actual electron stream performance from the theoretical ideal. Some additional correction has been obtained through use of the equalizing magnet assembly shown and described in my copending patent application entitled, Color Pure Cathode Ray Tube Display System and Color Purity Corrector Therefor, Serial No. 476,013, filed December 17, 1954.

In accordance with the present invention a color purity corrector is located on the conical bell portion of the cathode ray tube intermediate the electron gun or guns and the viewing screen. Briefly, the corrector includes a .band of non-magnetic material which encircles the axis of the tube in a plane normal to that axis. A plurality of permanent magnet units are mounted on the band in circumferential spaced relationship and are respectively rotatable about axes radially oriented in relation to the ,axis of the tube and axes in planes to the radial axes.

The unit produces an adjustable magnetic field of generally pie-shaped configuration as seen in the plane of the band, so that the field intensity is a maximum at the margins of the bell of the tube and becomes progressively weaker as. the axis is approached.

Adjustment of the respective magnets serves to control the orientation and intensity of the magnetic field within the tube envelope. This control automatically, however,

provides a magnetic field of decreased intensity as the tube axis is approached, and thereby aifects the electron beams in accordance with their position of sweep. Moreover, since the action takes place at locations between the electron gunsv and the shadow mask and viewing,

screen, the adjustments serve to deflect the electron beams in fashion serving the same overall function as the purity magnet assemblies heretofore used. In substance, the

action of the respective magnets is to cause the electron.

beams to act as if they originated at the theoretical design center of the tube, thus giving rise to faithful color rehave fixed axes generally parallel to the axis of the tube, and means is provided to vary the intensity of the spaced magnet poles they define.

It is therefore -a general object of the present invention to provide an improved color purity correcting device.

and system using the same for a color cathode ray tube which serves to provide color purity correction in a single unit.

Another object of the present invention is to provide a color purity corrector and system using the same which is located on the bell of the cathode ray tube and is within the confines of the enlarged end of the bell of the tube.

Still another object of the present invention is to provide a color purity corrector and system using the same which uses a plurality of magnets so arranged that a magnetic field is created of progressively decreased. intensity as the tube axis is approached.

Another object of the present invention is to provide" color purity correction devices and systems utilizing-the same which are capable of shifting the ray beams in anydirection and to any extent (up to a maximum) from the initial position.

It is yet another object of the present invention to pro- I vide color purity correcting devices and systems using the same which serve to provide color purity correction in a highly efficient manner.

It is yet another object of the present invention to provide a color purity corrector and system using the same which is of simple construction, utilizes only permanent magnets of readily obtained types, can be inex pensively manufactured, is readily applied to various tube and receiver constructions, and permits control of both radial and circumferential cathode raybeam deflection and the extent of each.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, together with further objects and advantages thereof, will best be understood by reference to the following description taken in connection with the accompanying drawings in which:

Figure l is a top plan view of a cathode ray tube for This color TV-"reception of the type to which the present invention is applicable, togetherwith the associated raybeam d'efiection and adjusting mechanism and the post deflection color field purifier mechanism of the present invention; 7

Figure 2 is an axial elevational viewiof thef color 7 purifier of'the present invention;

Figure 3"is' a fragmentary enlarged'viewii -perspective showing" a portion of the mounting strapjof the' meoh as nism and one of the adjustable magnet' units;

Figure 4' is; a top plan view of the portion" of the mechanisrn shown inFigure 3 and'ishowing' by dashed lines'an alternativejposition ofbracketadjustment;

Figure Sis' a crossfsecti'onal view through" axis: 7;

by the electron beam emanating from the corresponding electron gun-14g,-1 4r,- and14b; V r

In. operation, the electron streams from the guns are modulated in" accordance with the instantaneous intensities of blue, red and green col'oi to be produced as the television-image isascanned; These?time;-varyingelectroni beams aresweplt inunison over the;face v oftheishadew mask 20 andiphosphor plat'e' lfi byrsui'tablesweepcurrent ifiow in the defiection yoke;1 6. Ass-this takessplace, the ray beams are internuptedabylthmshadow mask 20 to Figure 4* and showing by dashed lines" an alternative position of magn'etzadiu's'tmentg V V i u 6? si 'd x mm ti' j ui pe n i h wm how thecathode ray' tubieiofFi'gure' Iis'erves to reproduce' a tel'evision'image in fullicolo r;

Figure 7' is a a diagrammatic vi'eWshovingtlietype of" magnetic field requiredfor radialjdeflction oftlie cathode ray beam over various positionstof ray beam'sweep; Figure; is. a? similar" diagrammatic view 'showinghow tlie'nrechanism' of the presentinventi'ontends to produce thedesired magnet field;

ajco'nvexfrontface.plate 10c'as' shown; A socket 12 is afiixed to the made? the necldport-ion- 1021 to make electrical connection with the socket prongs (notshownf which protrudeflfrom' the nec'lzf portion to connect-to'the various elements" within the tube: As" indicated by the dotteddines; there is provided' a phosphor plate 18'; here" inafter' described in detail," within the confines" of" the; envelope 10 and'immediately behind the face-plate 10%: In'addition, a. shadow mask ifl"isinterposedbetween'the phosphor-"plate"li and-the neck portionltl'wof'the tube, the mask 20.being jcomparatively close" to the phosphor pliitelfiandcdactir'rg: with the phosphor plateto givei colorrpicture reproduction' a's hereinafter described;

The cathode ray tube-has. a series of-threespaLeed electromguns shown intFi gure 9? These are spaced' equal 'radi'al' distances from'the tube'axis" and alongrradii IZO-apart. These electron gnns' areresp'ectively'indicated at 14,b,- 14g, and 14r, thedesignations b g,=and' fr indicating that the el'ecnonstreams'fromthe guns energizei'the blue, green andiredphosplrorsas hereinafter described: It will be r'iote'd'that the three electron guns arerlocated in spaced positionr within theneclifiof the tube andr rarerorie'ntedr in direction parallel to the axis oft tube; Consequently, asthe ray beamsare deflected i-n unis'on by the 'saw tooth-currents injthe coils of the deflection-yoke 1 6, thebeamsapproach the shadovv mask- 2 0{ andithe phosphor plate;18 from three separatedirec: tions.-. This-gives rise 'to ,thecolorsensitivity of the tube as described hereafter.

Figur a;;6;.shows in schematicand ig reatly enlarged :frag- V mentany'fornnthegshadow mask and phosphor .platet con struotion; "It beEobservedihat-the shadow 20.-

cause them vtorstrikefonly thephosphor dots corresponding to the color to be reproduced? This" color selective action'results from the-fact that-thethree electron guns are physically spaced in a plane normal to the axis of the tube. 1 Consequently the; electron" sn'eamsapproach the shadowf matskiandiphosphorjscreen"fromslightly difi ferent' directions; thus. causing; the. illuminated. space" behindeacliwindowflkr oftlr'e shadow "mask' to' be: dif ferent foreach" color: Incomequence, each electron" beam strikes-only the phosphor dots producing itsparticular color" and the TV image is reproducew'in full color.

Inthe' operation tricolor-television cathod'etray tubes" of" the ahove=discussed. type, it 'is necessary' that". the ray? beams approach theshadow maskrmsuch' direction ,asto" producefirll" color: That isierrorsih: therplrysical" con struction of'the tube, fbrexample; can'causethe green electron beam to strike the red or blue phosphor 'dots; or-vice versau When this. occurs; the wrong color" is reproducedand'tlie image degradedaccordingly: Irnper= fectionsini other portions of the" mechanism and stray' magnetic'fields'carrproducelkeidefectsI lirthe mechanisnr of the presentinvention; there is provided a'non-ma'gnetic'strap 22which isoffconical com by the" ears 22a" which" receive-fa bolt 2'4 and" not 2 52:.

to clamp theistra'p snugl'y'about theftube' and thereby" hold itfirmly in'position: Thesttap-may-be-ofalhmh num; forexample; andfelt-or rubber feet (notshown) ma'y' be' sandwiched between the strap an-ddhe' tubeto' take up the-= pull of the strap and" provide a A= plurality of 'adjustable'magnetunits; indicated generah 1yat 25; are disposed aboutathe periphery ofthe strap atuniform angular spacings asshown' in- Figures Paint 21 Eacli-- of these units; consists of an" angle-bracket- 26" havinga base-part 26a -andan upstandingpaxt 26b? The base part-Zfiuof each braeket is pivotally attachedto'the face ofth'estrap 22" by a suitable rivet 28% or: similar attachingmeans as shown: The upstandingportion-265* of" eaehbracket receives -a' shafb- 30Ywhich is-rotatahly held"by-"suitable means to the-portion 26d: At its-out board end'ea'chshaft 30 receivcsa=magnet 32? Asshown in Figure'3'; One-endfiZivof'the magnet is-magneti-zed to -form anortfipole andtliebtherend 3212 is magnetized used if-desiredtoapush the magnet SZ to'm-aXimum spaeed position in-;relation* tothe upstanding portion 26b of the bracket-'26: With thieconstiuction, theqend 30cvof the fit in a -suitable holein the-part 26b ofi-the bracket-26,-

a's the push of spring- 34 and the action of the head lvfia will serve to hold-the shaft-in a direction: normal-. 'tol' the planefof the part 26b of thebracket. r t

It will be noted that, insofar as movementcofranyof magnetssfaz is desired alon'g axesshavingalgenerally radial dispositiondn relation tozthe: A- A ,Figurel,

has laaplurality-iofz holes jtlgzdisposed ina uniform geoof-the tube, the-=braekets- 26 maybe rotated bodily around:v the respective -pinszii as shown by the dotted: lines of: Fi'gln'e" 4. This varies the orientation of the magnet-id fild's in the general direction of' 'ray beam travelr If the magnets are -desired to be rotated about=axes--trans= vrse tot-the axis clefined by v the respectivepins Z V the:

magnets may be rotated with shafts 30 as shown by the dotted lines of Figure 5. In either event the necessary rotation is eifected by hand manipulation of the parts.

The field obtained by the assembly of Figure 2 decreases in intensity as the center of the tube is approached. Consequently the tendency to deflect the electron beams is least along axis A-A, Figure 1, and increases as the electron beams are deflected from that axis under the action of the beam sweep mechanism. This is highly desirable since the necessary correction of the direction of ray beam travel is increased as the ray beam departs from the axis of the tube. In order to effect such correction, it is desirable to have a magnetic field of intensity varying generally as shown in Figure 7, where the concentric lines 36 represent units of magnetic flux and the axis shown is that of the tube. This type of field is not physically possible to produce, especially by the apparatus disposed outside the confines of the tube. However, the apparatus of the present invention approximates such field due to the action shown in schematic fashion in Figure 8. As shown in Figure 8, each of the magnets 32 produces a fringing magnetic field as indicated by the flux lines 32a. These lines can be considered to combine be tween adjacent magnets to produce what amounts to a continuous series of circumferential flux lines in the tube similar in form to those shown in Figure 7. Because the fringing fields become less intense as departure is made from the magnets-and hence as the axis of the tube is approached-the flux concentration falls as the tube axis is approached. This is the desired condition of Figure 7.

Since the maximum. corrective beam movement required is only the distance between one phosphor dot and another, the amount of required shift of the image is very small. In present tubes, for example, the distance between phosphor dots is about .029 inch, so that the requisite movement is small indeed. Moreover, in the usual course of events, the amount of the displacement required at the center of the viewing screen is about the same as -at the edge. The varying magnetic field described above in connection with Figures 7 and 8 serves to provide such displacement inasmuch as the beam angle changes as the beam moves from the central axis A'-A outward, and varying field strength tends to compensate for the inverse variations of ray beam deflection that would otherwise take place.

For full correction of the ray beam travel itis necessary to shift the beam or beams either radially or circumferentially, or btoh. The apparatus of the present invention does this. Insofar as the magnets are oriented as shown in Figure 8, the ray beam shift is radial, since the direction of electron motion is at right angles to both the direction of ray beam travel and the direction of the magnetic field. Insofar as the magnets are oriented with their flat faces facing the front or rear of the tube, rotation of any magnet will shift the ray beam (and hence image dot) about'a circular orbit. This rotation of the magnets is shown diagrammatically at 32 and 32b, F gure 8. As each magnet is rotated about its respective pivot pin 28, the orbit of ray beam shift becomes progressively more elliptical and finally degenerates to a straight line. Figures 10a to 10 inclusive, show the various orbits through which rotation of a magnet shifts the ray beam. Figure 10a shows a circular orbitprovided whenthe face of the magnet is facing either the base or the face of the tube. orbit-obtained when the face of the magnet is at right angles to the position of Figure 10a. Figures 19b to 10e are elliptical orbits obtained when the magnet is rotated about the pivot pin 28 from the position giving rise to the circular orbit of Figure 10a to that giving rise to the linear orbit of Figure 10 It will be observed thatthe action of all of these adjustments is to provide a positioning of the ray beam deflection from initial position (the center of the circle of Figure 10a) to any radius and in any direction within the confines of the circleof Figure 10a. Universal adjustment accordingly achieved.

Figure 10 shows a linear The position of the strap 10 in relation 'to the longi tudinaldirection of the tube 10' is not critical. Preferably it should be approximately on the focal plane of the ray beams. This is the plane where the ray beams converge to substantially a point. However, the focal plane itself is only a theoretical conception and experi ence has shown that the apparatus of the present invention serves its purpose over a considerable range of positions. It is important, however, to position the device between the deflecting yoke 16 and the shadow mask 20, and preferably about half way between. In this position, the extent of the ray beam sweep is limited and the device can usually be physically accommodated without undue difficulty, while at the same time the necessary ray beam correction is readily obtained. 7 Since the corrections required usually vary over the face of the shadow mask 20 and phosphor screen 18, the adjustments of the respective magnets will also usually vary about the periphery of the band 22. For purposes of illustration, such varying positions are shown in Figure 2.

Figures 11 to 13 show an alternative structure by which the position of the ray beam may be shifted as desired. In the construction of these figures, the bracket 126 is non-rotatably mounted on the support'strap 22, so that the faces of magnets 132 and 133 face either the base or the face of the tube. The two magnets 132 and 133 are of like construction and are mounted on the common shaft 130 as is shown in Figure 13, the magnets being rotatable on the shaft so that they can be rotated from the aligned position of Figure 11 to non-aligned positions such as that of Figure 12. The ends of the magnets each define opposite magnet poles. Since the magnets in this instance are position to face either the neck or the face of the tube, their rotation in unison will serve to move the ray beam from initial position about a circular orbit, such as that of Figure 10a. However, the intensity of the magnetic field in each instance is determined by the relative positions of the magnets 132 and 133being a maximum when they are aligned with like poles adjacent each other and being a minimum whenthey are aligned with opposite poles adjacent each other. The overall effect, therefore, is to provide ray beam shift about a circular orbit in each instance and having an adjustable radius. Thus the position of the ray beam shift can be varied in direction and extent to reach any position within the circular orbit defined by the magnets with their like poles adjacent each other.

In all of the constructions discussed above, the efficiency of the magnets is increased by providing a tilt to the respective shafts 30 (130, Figures 11-13) such that with the magnets facing either the face or the base of the tube, the axes define a cone generally parallel to the positions of the electron beam or beams at the most extended sweep positions. It is for this reason desirable to use a strap 22 of generally conical conformation fitting snugly on the envelope of the tube, since the tube envelope itself is generally coextensive withthe positions of the ray beams at maximum sweep. And by the use of such a construction it is possible to position the axes of the shafts 36 (130, Figures l113) in their most effective locations without the use of special tools that might otherwise be required.

The apparatus of the present invention perm-its the complete correction of the ray beam travel in a single unit, as distinguished from the previous use of both a color purity magnet located on the neck 10a of the tube and a second correcting device located generally in the plane of the phosphor plate and shadow mask. This has a number of advantages. It permits the adjustment of the correction without a multiplicity of interrelated correcting movements. It reduces the cost of the overall construction. It serves to free valuable space along the neck 10:: where numerous auxiliary correcting. devices (not shown) are normally used. In addition, the device is located on the conical portion of the viewing scr en where there .is n ual y sp e a ailable an i i unnecessarytq increas ;.th cabinet si e t ee mmodat tnegcorrecting: mechanism 7 V r t .111 the-appended, claims 51' haverejferred to the cathode rayrtuh a havin a general y conic l envelope to indicate that it :flaresoutwardly from the neck :to the region of the viewingscreen ,IIIQSQIIIE tubesthe crosssection departs frorn-a circle andris to that ,extent a dep t ur fr mrthe strict y -.conica :f nn, alth u erally onical withinthe m aning o eth la ms- :Al th n-' Yelope of the tube, whether literally conical orgenerally conical, forms ,a rsurface agljacent each magnet referred to whichsuriaeedefi e an elemen cfthecene. 1n th appended claims} hayegalsoreferred ,to the construction of Figures 11,-13 ;as ,prov iding a plurality of niagnet nits whichzserve-todefineoppcs dmagne pole cfadi, bl intensi y tor-streng ht illbe,.n ec1.: n th s nn ction th t, wha ever-the relatiye posi ion f th magne .132

audtzlfiahey do inpopiflilflifi dt Gh;P Q Qtber constructions, suchas magnets ,with shunting-shoes, may be usedjfidesired. j

Whil 7. hav sh n and es rib d cspeei i emb d m n s ogfthe pr ent inve ti nandtwith resp etta pecifi tub typ 'wil i f o rs be unders oq ha soth V modifications :and alternatives 1111 3" bellsed without d epa t ng i om t e trn xsn r t ,an scop th eo 1 a d t at h i ventienmmay beapplied t any tub w erein co rection of ,ray beam position is desired. In; particular,

other means may be used to mount'jthe magnetsior subs an ially nui er l m v men ina ring abo th -.t '0n caln r ion. f :t e tu oth r cons ruct o m y be nee to provide the necessary adjnstabiiity, and disk or other s aped-magne s mayb aused-in l eu fthe :barmagn t shown. I therefore intend by the appendedclaims to 7 cover all such modifications and alternative constructions t a f wi in th i ue sh t-i and. sco e Wha in1 n weand desir fQ'l E'FbYLLflt IS Patent oi the United Statesjs:

' 1n combin tion, 1 @91 1 lv j-ea d ir y :mb a

the. ype h v ng lea on l ctro g tedante t prod ce an electron streamgnarel e t e ax f t tub when s n fl ted; an a vi wi g ereen. ad pted-its receive the raybearn and reproduce an image-ps it is swept over th i cr en e ub further :be n o h typegwhereincfaithful :color reproduction :isgobtained only when the ray beam appears to ori-ginatejrgm a predetermined design center ofithe tube; a band cinch-magnetic 'nraterial encircling and-coaxial'with the tube locatecl between theelectron gun-and the viewing screen; a plurality Y of support, brackets mounted onysaid bandat substantialiy ,egual circumferential spacings and rnounted for wivableg movement abo axe radia y. di pQ$ d-.- n,re1ation :to ith band, achbr ske havi g :a wrt cmex n ii g radially utw r .f m t b nd; and a permane ma e sloeated 10.11 c s o th las p r on 1 of 1; h

I bra ts, spectiv ly,-. th mag et bein rotatabl uut "axe vnormal t t ax w abl moveme c th suppe br ek whereby th r y be m ra m y b adjustabiy corrected in b oth radial and circumferential termined design i adi ee t pprtiqn ef the u e .=e v gpe,l a vmeans ug rotatable" about an. n rm to aa aam be S f the-tu envelep there y creating ee re a magn ic fiel 7 c eas gin en ityas th is '23P" p e he an means located betwe nsai Pe manen magnets and the electron gun .to-sweep'the; beam over the face of the viewingscreenas gr-i n from said desig ce r to on tit t -ieelq :nicture thereon de p imp rfecti n in thetsy tem .3- In' mb t n, :a c or T eatbqd view-9 the typ vi an ax sat leas o relecttqnssunz opte t Produc a ee en s ampa llto th 8 9f th ub hen lun efi cted and a ew n s r eniadap d t rece v th .ray bea and reproduc an imae i sweptv e r ,tbesser en, the tub furth being o th typ where n :iaithfu c lo rep o uct on i pht ned n y wh n the say s izner- 4 .926533 s pported for univ rsal :a i tmen 19in sc, lectable positions inrelation to ,an axis radial to-;the;.axis

' ofthe tube and inrelationtozana isgenerallylnarnllfi to the adjacent portion of the tube -envelope;-;and gneans located between the said ,zpermanent qrnagnets sand the electrongun to sweep the:electr.onrbeam over the-face of the viewing :screen as, i originating from said ;des ign center to reconstitute a color TV.-;pictur,e ithereomaiespite imperfections in'thesystem. 7

4. In combination, a color- TV cathode -ray,tube;;0 the type :having a generally conical; envelope defining :;an axis, :at leastone electron-gun adapted to-produce :an electron-.streamparallel to the -axis iofth'e itube when-pndeflected, man viewing screen adapted .to--reeeiye nhe ray beam' and-:reprodueeean imagesastit-is swept-rover the screen, tbe tube-further being of the typeiwher'ein faithful color reproduction is obtained .only-when the ray beam appears to originate from =a-predetermined design center of thetube; a correcting device comprising a band'of non-magnetic,-rnaterial5ofngenerally conical conformation adaptedr to fit on-the said conical portion of the tube and deflection meansIQcated betWeensaid band-and the electron gun, the-bandhaving auplurality the screen, ,the tube further being of the type wherein V faithfulrcolor reproduction ,is obtainedonly when the ray beam-appears: to originate-from a predetermined: de-

7 sign center ,of the tubepmeans including a plurality of circumieren i ll-y sp ed-p rmanen m tme sv dispose :in

a concentric with, the. axis of, the tube and ina plane gen rally; normal t ;th .th tmas et specti e y .be ng rqtatabl about, an gen ral y pa al e e-V. th

of permanent -magnets --circun iferentia1ly spaced therearound and individually mounted on said band for swivablemovement about an axisnor-mal to tbe adacent-tube surfaces and axes; normal "thereto :to-shift the ray -beain as; required to -make -'-it -appear-tooriginate from the design center of the tube "when swept over; the viewing screen. a e '5. A post deflection color purity correcting device for a 1 color "cathode ray tube ;of-the t ype having a gen erallycqnical envelope defininganaxis, the devicec0mprising: a conicaLn n-magnetic-strap adapted-to be'received on the enyelope-of-said tube-aplutalit'y of brackets mounted on saidstrapior -swivabl e-move-menton an axis radial'to'the axis of the envelope, ancia permanent magnet mounted I on :each 1 bracket for rotation abontan axis normal to' the axis ofmovementof-thebracket.

Reference fl te n tbefi e p tent UNiTE-D STATES PATENTS 

